Zaimanhua: Improve comment rendering (#10340)

- Better text layout and spacing for comments.
- Ensure the generated image is not too short, to avoid being displayed as a double-page spread.

src/zh/zaimanhua/build.gradle

@@ -1,7 +1,7 @@
 ext {
     extName = 'Zaimanhua'
     extClass = '.Zaimanhua'
-    extVersionCode = 11
+    extVersionCode = 12
     isNsfw = false
 }
 

src/zh/zaimanhua/src/eu/kanade/tachiyomi/extension/zh/zaimanhua/CommentsInterceptor.kt

@@ -3,6 +3,7 @@ package eu.kanade.tachiyomi.extension.zh.zaimanhua
 import android.graphics.Bitmap
 import android.graphics.Canvas
 import android.graphics.Color
+import android.graphics.Typeface
 import android.text.Layout
 import android.text.StaticLayout
 import android.text.TextPaint
@@ -13,21 +14,26 @@ import okhttp3.Response
 import okhttp3.ResponseBody.Companion.asResponseBody
 import okio.Buffer
 
-fun parseChapterComments(response: Response, count: Int): List<String> {
+fun parseChapterComments(response: Response): List<String> {
     val result = response.parseAs<ResponseDto<CommentDataDto>>()
     val comments = result.data.toCommentList()
     return if (result.errmsg.isNotBlank()) {
         throw Exception(result.errmsg)
     } else {
-        comments.take(count)
+        comments
     }
 }
 
 object CommentsInterceptor : Interceptor {
     private const val MAX_HEIGHT = 1920
     private const val WIDTH = 1080
-    private const val UNIT = 32
-    private const val UNIT_F = UNIT.toFloat()
+    private const val X_PADDING: Float = 50f
+    private const val Y_PADDING: Float = 25f
+    private const val SPACING_MULT: Float = 1f
+    private const val SPACING_ADD: Float = 0f
+    private const val HEADING_FONT_SIZE: Float = 36f
+    private const val BODY_FONT_SIZE: Float = 30f
+    private const val SPACING: Float = BODY_FONT_SIZE * SPACING_MULT + SPACING_ADD
 
     override fun intercept(chain: Interceptor.Chain): Response {
         val request = chain.request()
@@ -35,46 +41,85 @@ object CommentsInterceptor : Interceptor {
         if (request.tag(String::class) != COMMENTS_FLAG) {
             return response
         }
-        val comments = parseChapterComments(response, MAX_HEIGHT / (UNIT * 2) - 1).toMutableList()
-        comments.add(0, "章末吐槽：")
 
-        val paint = TextPaint().apply {
+        val paintHeading = TextPaint().apply {
             color = Color.BLACK
-            textSize = UNIT_F
+            textSize = HEADING_FONT_SIZE
+            typeface = Typeface.DEFAULT_BOLD
             isAntiAlias = true
         }
 
-        var height = UNIT
-        val layouts = comments.map {
+        @Suppress("DEPRECATION")
+        val heading = StaticLayout(
+            "章末吐槽：",
+            paintHeading,
+            (WIDTH - 2 * X_PADDING).toInt(),
+            Layout.Alignment.ALIGN_NORMAL,
+            SPACING_MULT,
+            SPACING_ADD,
+            true,
+        )
+
+        val comments = parseChapterComments(response).toMutableList()
+        val paintBody = TextPaint().apply {
+            color = Color.BLACK
+            textSize = BODY_FONT_SIZE
+            typeface = Typeface.DEFAULT
+            isAntiAlias = true
+        }
+
+        var currentHeight = Y_PADDING + heading.height
+        val bodyLayouts = mutableListOf<StaticLayout>()
+        for (comment in comments) {
             @Suppress("DEPRECATION")
-            StaticLayout(it, paint, WIDTH - 2 * UNIT, Layout.Alignment.ALIGN_NORMAL, 1f, 0f, false)
-        }.takeWhile {
-            val lineHeight = it.height + UNIT
-            if (height + lineHeight <= MAX_HEIGHT) {
-                height += lineHeight
-                true
-            } else {
-                false
+            val layout = StaticLayout(
+                comment,
+                paintBody,
+                (WIDTH - 2 * X_PADDING).toInt(),
+                Layout.Alignment.ALIGN_NORMAL,
+                SPACING_MULT,
+                SPACING_ADD,
+                true,
+            )
+            val lineHeight = SPACING + layout.height
+            // If adding this comment doesn't exceed the max height, add it.
+            // If it does exceed and it's a single line, stop adding more comments.
+            // Otherwise, if it's multi-line, just skip it and try the next comment.
+            if (currentHeight + lineHeight <= MAX_HEIGHT) {
+                bodyLayouts.add(layout)
+                currentHeight += lineHeight
+            } else if (layout.lineCount == 1) {
+                break
             }
         }
 
-        val bitmap = Bitmap.createBitmap(WIDTH, height, Bitmap.Config.ARGB_8888)
-        bitmap.eraseColor(Color.WHITE)
-        val canvas = Canvas(bitmap)
+        // The bitmap height must be no more than MAX_HEIGHT
+        // and no less than its width to prevent automatic double-page splitting.
+        val bitmapHeight = (currentHeight + Y_PADDING).toInt().coerceIn(WIDTH, MAX_HEIGHT)
 
-        var y = UNIT
-        for (layout in layouts) {
-            canvas.save()
-            canvas.translate(UNIT_F, y.toFloat())
-            layout.draw(canvas)
-            canvas.restore()
-            y += layout.height + UNIT
+        val bitmap = Bitmap.createBitmap(WIDTH, bitmapHeight, Bitmap.Config.ARGB_8888)
+        Canvas(bitmap).apply {
+            drawColor(Color.WHITE)
+            heading.draw(this, X_PADDING, Y_PADDING)
+            var y = Y_PADDING + heading.height + SPACING
+            for (layout in bodyLayouts) {
+                layout.draw(this, X_PADDING, y)
+                y += layout.height + SPACING
+            }
         }
 
         val responseBody = Buffer().run {
-            bitmap.compress(Bitmap.CompressFormat.JPEG, 90, outputStream())
-            asResponseBody("image/jpeg".toMediaType())
+            bitmap.compress(Bitmap.CompressFormat.PNG, 0, outputStream())
+            asResponseBody("image/png".toMediaType())
         }
         return response.newBuilder().body(responseBody).build()
     }
+
+    @Suppress("SameParameterValue")
+    private fun StaticLayout.draw(canvas: Canvas, x: Float, y: Float) {
+        canvas.save()
+        canvas.translate(x, y)
+        this.draw(canvas)
+        canvas.restore()
+    }
 }